Titanium base alloy



United States Patent 2,726,954 Patented Dec. 13, 1955 tween 0.1% and 0.3% of carbon, with or without 0.01% to 0.15% nitrogen or 0.01% to 0.25% oxygen, or both 2,726,954 oxygen and nitrogen, is generally quite beneficial. Among the alloys of this invention are those made either TITANIUM BASE ALLOY 5 with a commercial titanium base meeting such specifi- Robert I. Jaifee and Horace R. Ogden, Columbus, Ohio, Cations, Wit-l1 a g P y titanium base Containing assignors, by mesne assignments, to Rem-Cru Titanium, similar amounts of added carbon, oxygen and/or nitro- Inc., Midland, Pa., acorporation of Pennsylvania gen. Thus, within the purview of the invention are A ternary alloys containing from about 2% to about 7% alu- No m ggf ig g g 1947 10 minum and up to about chromium, as additions to a titanium-base which may be of high purity or may con- 11 Claims. (Cl. 75-1755) tain up to 0.15% nitrogen, 0.25% oxygen and/or 0.3%

carbon; the total nitrogen, oxygen and carbon content preferably not exceeding 0.5%. Also within the purview of This invention relates to novel titanium-base alloys hav- 15 t i e tion a e q a ern ry alloys containing up to about ing properties which render the alloys highly useful for 5% aluminum, up to 1.25% chromium, and up to 1.25% structural purposes. molybdenum, as additions to the same titanium bases. In a companion application, Serial Number 122,577, The physical properties of illustrative ternary alloys filed October 20, 1949, now Patent No. 2,554,031, granted based on high purity titanium with various additions of May 22, 1951, the present inventors have disclosed cercarbon, oxygen and/or nitrogen, as hot rolled and antain structural alloys which include the addition of a few nealed at 850 C., are given in the table below, in which percent of molybdenum to a titanium-base alloy containthe proportional limit, yield strengths and ultimate strength ing from about 2% to about 8% at aluminum. are in units of thousands of pounds per square inch.

Tensile Properties Composition TI Bass A1 Cr Vickers Prop. 0.1% 0.2% Ultiiggly: 522 Hardness Limit Ofiset Ofiset mate tigr in ducflon 5 1.0 270-310 62 92 100 115 11 5 2. 5 280 94 99 100 118 12 22 5 2. 5 330 119 124 124 13s 9 20 5 2. 5 347 132 138 138 150 10 27 5 2. 5 382 142 150 151 159 e 5 5 2. 5 401 150 159 160 170 12 27 5 3. 5 340 121 129 130 143 12 2s 5 5.0 313 92 104 100 123 12 36 5 5. 0 354 127 130 131 142 12 2s 5 10. 0 372 128 141 146 103 7 s 5 15.0 314 116 128 129 130 7 24 5 2.5 99 133 145 12 37 The present invention comprises the discovery that It will be seen that the minimum quantity of chrodesirable structural alloys of the general character of mium which has a material elfect is about 1%, that the those disclosed in said companion application may be optimum of chromium is about 2.5%, and that ternary made by the use of chromium, instead of molybdenum, alloys of titanium and aluminum with about 2.5% of as the ingredient added to a master titanium-base alloy chromium are benefited by the addition of carbon, oxycontaining a few percent of aluminum. gen and nitrogen, in the quantities in which these ele- The present invention comprises the further discovery ments are contained in commercial titanium. that, whereas the maximum permissible molybdenum Structurally, after annealing at 850 C., for 3 /2 hours, content is somewhat less than 10%, alloys containing as the alloys containing 5% chromium show relatively fine much as 15% of chromium show excellent strength propequiaxed grains of the alpha phase in a matrix of the beta erties and at the same time retain a ductility adequate phase. The alloys of 10% chromium content show a for structural uses. structure of large beta grains containing fine alpha nee- The invention comprises the further discovery that the dles in a Widmanstatten pattern. In the 15 chromium concurrent use of both chromium and molybdenum in a alloys the alpha phase has almost disappeared, only a base alloy containing aluminum is productive of high very smallamount remaining within the beta grains and strength alloys of adequate ductility. along the grain boundaries. As a stabilizer of beta ti- The titanium base metal used in the present alloys may tanium, chromium is more eifective than molybdenum. contain substances or impurities besides titanium, as nor- The alloys of lower chromium content harden as much mally found in either high purity titanium or commeras 95 Vickers points on quenching from a temperature of cially pure titanium. It may be, for example, a high 950 C. or higher, while those of higher chromium conpurity or iodide process titanium, as produced accordtent may quench soft, this effect being related to the staing to the Van Arkel U. S. Patent No. 1,671,213. Alterbilization of beta titanium. natively, it may be a commercial titanium, as produced, These alloys show excellent resistance to heat softenfor example, by magnesium-reduction processes, such as ing, and are thus particularly adapted for use at relatively the process of U. S. Patent No. 2,205,854, to Kroll, or high temperatures. For example, an alloy of 5% alumodifications thereof; provided that the carbon, oxygen minum, 2.5 chromium, 0.25% carbon, balance substanand nitrogen contents of these alloys, hence of the base tially all titanium, having a room temperature hardness metal, should not exceed 0.5%, 0.25 and 0.15% reof 352 Vickers, shows, at 400 F., a Vickers hardness of spectively, nor should they total more than about 0.5%, 270, and at 600 F., a Vickers hardness of 246. Thus, at if the alloys are to possess good ductility as cast or as 600 F., its Vickers hardness number has decreased by worked and annealed.

It has been found, however, that the presence of beabout At 800 F., the Vickers hardness is 226, and at 1000 F., it is 186, a figure comparable with the av- 3 erage room temperature hardness of commercial titanium. As above set forth, the optimum chromium content for alloys of this type is about 2.5 Alloys of comparable properties can be made by substituting molybde- 4 V num, about 2.5% chromium, about 0.25% carbon, about 0.1% nitrogen and about 0.1% oxygen, balance titanium.

6. An alloy composed essentially of 2%7% aluminum, 1%15% chromium, and the balance titanium.

particles dispersed intergranularly in a fine grained alpha matrix.

What is claimed is: 5 1. An alloy containing from about 2% to about 7% aluminum and from about 1% to about chromium, balance titanium.

2. An alloy containing about 5% aluminum and from about 1% to about 15% chromium, balance titanium.

3. An alloy composed essentially of 2% to about 7% aluminum, about 1% to about 15% chromium, and about 0.25% carbon, balance titanium.

4. An alloy composed essentially of about 5% aluminum, about 2.5 chromium, from 0% to about 0.15%

nitrogen, from 0% to about 0.25 oxygen, and from 0% to about 0.3 carbon, balance titanium.

5. An alloy composed essentially of about 5% aluminum for part of the chromium. As before, the presence 5 7. An alloy composed essentially of 2%5% alumiof some carbon, oxygen or nitrogen, is beneficial- Typinum, 1%-l0% chromium,- 0.1%-0.3% carbon, and the cal alloys of this character, and their properties after hot balance titanium. rolling and annealing atabout 850 C., are as follows: 8. A ductile titanium base alloy containing: about 2- 'lensile Properties Composition Annealed (Balanoe- Hard- Percent Percent Ti) ness Propor. 0.1% 0.2% Ultimate Elonga- Area Limit Oflset Offset Strength 7 tion in Reduc- 1 tion These alloys are of the two-phase type, titanium being 7% aluminum and about 1-15% chromium, the balance present in both the alpha and beta forms. Both chromiof the alloy being substantially titanium and said alloy um and molybdenum are within a group of metals which being characterized in high resistance to softening at tend to stabilize beta titanium at ordinary temperatures. elevated temperatures, and in having an ultimate strength The presence of beta titanium in the finished alloy has at least 10% in excess of that of the titanium base metal. been found beneficial in increasing both strength and 9. A ductile titanium base alloy containing: about 2- ductility. 7% aluminum, about ll5% chromium, up to about In the above table, certain elongation data are missing, 0.15% nitrogen, up to about 0.25 oxygen and up to due to the fact that rupture occurred at a location such about 0.3% carbon. H16 balance of the alloy being that accurate measurement of elongation was impractistantially titaniurnand saiclalloyhavinganultimate strength cable. Area reduction, however, gives an index of at least 10% in excess of that of the titanium base metal, ductility, and being characterized in high resistance to softening The physical properties of these quaternary alloys will at elevated temperatures. be seen to be comparable with, though slightly inferior Atitanillm base alloy consisting ssentially of about: to, those of the ternary chromium alloys. Structurally, all 2 0 7% aluminum d about 1 15 Chromium,

' of the quaternary alloys are similar, consisting of beta acterized in having an ultimate strength of at least 100,000

p. s. i. and a tensile elongation of at least 2%.

11. An alloy consisting of about: 2 to 7% aluminum, 1 to 15% chromium, up to 0.3% carbon, up to 0.25% oxygen,.up to 0.15 nitrogen, and the balance titanium.

OTHER REFERENCES Titanium Report of Symposium, Dec. 16, 1948, sponsored by Ofiic'e of Naval Research, pageslOS and 111.

U. S. Air Force Project Rand, Titanium and Titanium-Base Alloys, published by Battelle Memorial Institute, March 15, 1949, pages 11 and 13. 

1. AN ALLOY CONTAINING FROM ABOUT 2% TO ABOUT 7% ALUMINUM AND FROM ABOUT 1% TO ABOUT 15% CHROMIUM BALANCE TITANIUM. 